1. Field of the Invention
The present invention relates to a process for producing a urethane die for use in pressing and, more specifically, to a process for producing a urethane die having a resin layer made of a urethane resin and which corresponds to the shape of a punch which is inserted into the recess of the die.
2. Description of the Prior Art
Japanese Patent Application Laid-Open No. 176,426/1986 discloses a process for producing a die comprising inserting a punch into a recess formed in the body of a die so that a space is formed between the recess and the punch, and injecting a urethane resin into the space formed in the recess so that a resin layer in the shape of the punch is formed in the recess.
In the above-mentioned die, ribs are provided protrusively in the recess for the purpose of improving the bite, or adherence, between the die body and the urethane resin layer. However, the resin layer sometimes peels off from the die body in the case of repeated use. It may be possible to cope with this difficulty by preliminarily applying an adhesive to the inner surface of the recess to thereby bond the resin layer to the die body. In this case, however, the adhesive often degenerates to lower the bonding strength thereof because it is affected by heat generated during the hardening of the urethane resin. Additionally, because a urethane resin is sometimes subjected to a hardening treatment in a drying furnace or the like to promote the hardening thereof, there also occurs a problem of degeneration of the adhesive.